Mixed grain photographic emulsions



Patented Apr. 10,1951

MIXED GRAIN PHOTOGRAPHIC EMULSIONS Leopold'Godowsky, Jr., Westport, Conn., assignor' to Eastman Kodak Company, Rochester, N. Y.,- a. corporation of New Jersey No Drawing. Application December Serial No. 715,605

6 Claims.

This invention relates to color photography and particularly to mixed grain photographic emulsions.

There have been numerous prior suggestionr of mixed grain photographic emulsions, that is photographic systems in which differently sensitized silver halide grains are incorporated in a single photographic emulsion layer and may be used to produce differently colored photographic images in the layer. Mixed grain photographic systems have a number of advantages among which are the simplicity of coating a single photographic layer and the improvement in definition secured by having the differently sensitized particles juxtaposed in a single layer. Processing the emulsion is also generally simplified.

Prior mixed grain photographic methods have not been successful because it was impossible to secure color separation, that is, to prevent color development of the silver halide grains which had not been exposed.

I have now found a mixed grain photographic method by which color separation can be secured and differently colored photographic images produced in a single emulsion layer. My method involves in general the incorporation of the sensitized silver halide grains and a color former or coupling compound in a colloidal material which is soluble in water but which may be rendered insoluble and dispersed in a water-permeable colloidal material such as gelatin or polyvinyl alcohol. The colloidal material in Which the silver halide and coupler are incorporated consists of a hydrophilic macromolecular compound, esspecially a polymeric six-carbon atomv aldehyde carboxylic acid such as alginic acid or oxidized cellulose. Alginic acid is a polymeric d-mannuronic acid and is available as the water-soluble sodium salt. Oxidized cellulose is a polymeric dglucuronic acid. The formula for alginic acid, of which algin is the sodium salt, may be represented as follows:

Other hydrophilic macromolecular compounds 2 molecular I mean a colloidal or "polymeric compound.

The general method for'the preparation of a mixed grain emulsion according to my invention involves the preparation of two'or more silver halide emulsions sensitive to diiierent regions of the spectrum. These emulsions may be prepared in gelatin as a carrier for the silver halide in the usual way or the silver halide may be dispersed directly in the algin or sodium alginate. If the silver halide is dispersed in gelatin the emulsions are separately mixed with portions of the sodium alginate. In either case, coupler is added to each emulsion and the emulsions are then mixed with gelatin or other water-permeable carrier containing a water-soluble salt of a metal capable of forming a colorless, insoluble salt with the sodium alginate. This forms an insoluble salt of the alginate, and the sensitized silver halide and coupler are retained in the insoluble salt of alginate thus formed. The mixture is homogenized, resulting in a dispersion in gelatin or other carrier used, of particles of insoluble alginate containing sensitized silver halide and coupler.

T'he water-soluble salt of a metal, used to form the insoluble alginate, may be calcium chloride, calcium acetate, aluminum acetate or Water-soluble salts of zirconium, barium, zinc or tin.

In the production of the alginate dispersions, it is generally simpler toprepare gelatino-silver halide emulsions containing couplers in the usual way. The coupler added to the emulsion may be one which is non-diffusing in the gelatinas described in British Patent 503,752 or the "emulsion may be prepared using a method such as that described in Jelley and Vittum U. S. Patent 2,322,027. The couplers listed in the Jelley and Vittum patent may be used in my process. The dispersion may also be made with the couplers described in Peterson U. @S. Patents-2,308,023; 2,296,306; and 2,353,754.. l 4 I It will be understood that the silver halide mulsions employed in my process "may be sensitized to the blue, green and red regions of the spectrum With non-wandering sensitizers in the customary manner. As a green sensitizer, 5- [:3'- ethyl-2-(3)-benzoxazolylidenel ethylidene 3- n-heptyl-l-phenyl-Z-thiohydantoin may be used,

and as a red sensitizer, 5.,4- [3-ethyl-2-(3) -benzothiazolilidinel -2-butenylidene-3 n'- heptyl l phenyl-Z-thiohydantoin (U. S. Patent 2,282,116) is suitable. It is an advantage, of course, to provide a single mixed grain layer containingffor example, the green-sensitive and red-sensitive particles and to coat as a separate layer anemul Emample 1 1 liter of a gelatino-silver bromide emulsion was sensitized to red light with the sensitizer indicated above, and a dispersion of cyan coupler in a di-n-butyl phthalate was added to the emul- Itwill be understood that the examples insion. This dispersion of coupler in red-sensitive silver bromide emulsion was prepared in the manner described in Example 1. of Jelley and Vittum U. S. 2,322,027 except that di-nbutyl phthalates was used in place of Veritrole.

To 100 cc. of the dispersion prepared in this way there was added 025 gram of Calgon in cc. of water and 0.5 of Quick-Mix algin (sold by Innis, Speiden Co., 121 Liberty Street, New York 6, New York) with rapid stirring. The algin dissolved readily and the emulsion-algin solution 7 was then added dropwise to a solution containing 7500. of 10% gelatin solution and 100 cc. of 0.5% calcium acetate solution with very rapid and efiicient stirring. After all this had been added the suspension of calcium alginate particles in gelatin were put through a colloidal mill from 4 to 6 times.

To 1 liter of a gelatino-silver bromide emulsion sensitized to green light with the sensitizer indicated above, there was added a dispersion of 7 grams of a magenta coupler in di-n-butyl phthalate. This emulsion was prepared in the manner described in Example 3 of J elley and Vittum 2,322,027 using di-n-butyl phthalate in place of dimethyl phthalate. A 100 cc. portion of this emulsion was treated in the same manner as the red-sensitive emulsion described above.

The red-sensitive and green-sensitive melts were then mixed, coated and processed in the usual way. The developing solution described on page 5 of U. S. Patent 2,822,027 was used for de velopment of the exposed material.

Example 2 The general procedure of Example 1 was followed except that calcium acetate solution was added to the plain gelatin solution through a very fine orifice and the emulsion in algin solution was added dropwise simultaneously into the same gelatin solution always keeping the calcium acetate solution in slight excess in the reacting medium. The dispersion prepared in this way was coated, exposed and developed.

Example 3 I To 100 cc. of a red-sensitive gelatino silver bromide-emulsion prepared as described in Example 1, there was added 1.0 gram of algin which was thoroughly stirred into the emulsion. This mixture was then added to 100 cc. of 5% gelatin solution in a Waring Blendor running at high speed. After a minute or two, 10 cc. of 10% calcium acetate solution were added and stirring was continued for about two minutes.

The same procedure was followed and the green-sensitized emulsion containing magenta coupler prepared as described in Example 1.

The two materials were then mixed, coated and processed in the usual way as described in Example 1.

In each case a distinction was observed between theportions of the coating which were exposed to green light and portions which were exposed 4 to red light. The appropriate color was produced in each region of exposure.

While I have described negative processing of the emulsions, it will be understood that processing may also be carried out by reversal. After ordinary black-and-white development, the mixed grain emulsion is flashed with white light and again developed, this time in a color-forming developer. Silver removal and fixing complete the process.

cluded herein are illustrative only and that my invention is'to be taken as limited only by the scope of the appended claims.

I claim:

1. A sensitive photographic element comprising a single emulsion layer capable of reproducing colors of different regions of the spectrum,

said layer comprising a water-permeable colloidal material containing particles of insoluble salt of a polymeric G-carbon-atom aldehyde carboxylic acid 1 having dispersed therein silver ha ide grains sensitive to a region of the visible spectrum and a color former capable of coupling with the oxidation product of a primary aromatic amino developing agent to form a dye image, and at least one other group of separate particles of said insoluble salt having dispersed therein silver halide grains sensitive to a different region of the visible spectrum than said first-mentioned grains and a color former capable of coupling to form a different dye image than said first-mentioned color former.

2. A sensitive photographic element comprising a single emulsion layer capable of reproducing colors of different regions of the spectrum, said layer comprising a water-permeable colloidal material containing particles of insoluble salt of alginic acid having dispersed therein silver halide grains sensitive to a region of the visible spectrum and a color former capable of coupling with the oxidation product of a primary aromatic amino developing agent to form a dye image and at least one other group of separate particles of said insoluble salt having dispersed therein silver halide grains sensitive to a difierent region of the visible spectrum than said first-mentioned grains and a color former capable of coupling to form a different dye image than said first-mentioned color former.

3. A sensitive photographic element comprising a single emulsion layer capable of reproducing colors of diiferent regions of the spectrum, said layer comprising gelatin containing particles of calcium alginate having dispersed therein silver halide grains sensitive to a region of the visible spectrum and a color former capable of coupling with the oxidation product of a primary aromatic amino developing agent to form a dye image, and at least one other group of separate particles of said calcium alginate having dispersed therein silver halide grains sensitive to a different region of the visible spectrum than said first-mentioned grains and a color former capable of coupling to form a difierent dye image than said first-mentioned color former.

4. A mixed grain photographic emulsion comprising a gelatin layer having dispersed therein particles of insoluble salt of alginic acid containing red-sensitive silver halide grains and color former capable of coupling with the oxidation product of a primary aromatic amino developing agent to produce a cyan dye, and separate particles of insoluble salt of algin containing greensensitive silver halide grains and color former capable of coupling with the oxidation product of a primary aromatic amino developing agent to form a magenta dye.

5. The method of forming a mixed grain photographic emulsion which comprises dispersing in a gelatino-silver halide emulsion sensitized to a region of the visible spectrum, a color former cap-able of coupling with the oxidation product of a primary aromatic amino developing agent to form a dye image, mixing said emulsion with a water-soluble salt of a polymeric S-carbonatom aldehyde carboxylic acid to form a mixture, and dispersing said mixture in gelatin containing a water-soluble metal salt capable of forming a water-insoluble metal salt of said carboxylic acid, dispersing in at least one other gelatino-silver halide emulsion sensitized to a difierent region of the visible spectrum, a color former capable of coupling with the oxidation product of a primary aromatic amino developing agent to form a dye image difierent from said first-mentioned dye image, mixing said other emulsion with a second portion of water-soluble salt of polymeric S-carbon atom aldehyde carboxylic acid to form a second mixture, and dispersing said last-mentioned mixture ina second portion of said gelatin containing a water-soluble metal salt, and then mixing together each of the dispersions to form a mixed grain emulsion.

6. The method of forming a mixed grain photographic emulsion which comp-rises dispersing in a red-sensitive gelatino-silver halide emulsion, a color former capable of coupling with the oxidation product of a primary aromatic amino developing agent to form a cyan dye image, mixing said emulsion with algin to form a mixture, and dispersing said mixture in gelatin containing a water-soluble calcium salt to form calcium alginate, dispersing in a green-sensitive gelatino-silver halide emulsion, a color former capable of coupling with the oxidation product of a primary aromatic amino developing agent to form a magenta dye image, mixing said green-sensitive emulsion with algin to form a second mixture, and dispersing said last-mentioned mixture in a second portion of gelatin containing a watersoluble calcium salt, and then mixing together each of the dispersions to form a mixed grain emulsion.

LEOPOLD GODOWSKY, JR.

REFERENCES CITED The following references areof record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,168,182 Wendt Aug. 1, 1939 2,186,730 Schneider Jan. 9, 1940 2,284,877 Martinez June 2, 1942 FOREIGN PATENTS Number Country Date 541,511 Great Britain Nov. 28, 1941 541,514 I Great Britain Nov. 28, 1941 

1. A SENSITIVE PHOTOGRAPHIC ELEMENT COMPRISING A SINGLE EMULSION LAYER CAPABLE F REPRODUCING COLORS OF DIFFERENT REGIONS OF THE SPECTRUM, SAID LAYER COMPRISING A WATER-PERMEABLE COLLOIDAL MATERIAL CONTAINING PARTICLES OF INSOLUBLE SALT OF A POLYMERIC 6-CARBON-ATOM ALDEHYDE CARBOXYLIC ACID HAVING DISPERSED THEREIN SILVER HALIDE GRAINS SENSITIVE TO A REGION OF THE VISIBLE SPECTRUM AND A COLOR FORMER CAPABLE OF COUPLING WITH THE OXIDATION PRODUCT OF A PRIMARY AROMATIC AMINO DEVELOPING AGENT TO FORM A DYE IMAGE, AND AT LEAST ONE OTHER GROUP OF SEPARATE PARTICLES OF SAID INSOLUBLE SALT HAVING DISPERSED THEREIN SILVER HALIDE GRAINS SENSITIVE TO A DIFFERENT REGION OF THE VISIBLE SPECTRUM THAN SAID FIRST-MENTIONED GRAINS AND A COLOR FORMER CAPABLE OF COUPLING TO FORM A DIFFERENT DYE IMAGE THAN SAID FIRST-MENTIONED COLOR FORMER. 